Hydraulic internal gear machine having a fluid pressure biased sealing plate

ABSTRACT

A hydraulic gear machine, in particular an internal gear machine having two gear wheels which mesh with each other in a chamber of a multipart housing, a sealing plate arranged on the side of the two gear wheels axially between them and a housing part, and a pressure field which is present in the housing part on the high-pressure side, is open towards the sealing plate, and is adapted to be acted on by high pressure. The order to provide embodiments of the gear machine which differ in their direction of rotation with the use of many of the same parts, a second pressure field is present in the housing part and the first pressure field is present only on the one side and the second pressure field only on the other side of a center plane which is defined by the axes of rotation of the two gear wheels so that a piece of the housing part is still present between the two pressure fields. Of the two pressure fields of a housing part, only the one pressure field can be acted on by high pressure in the specific counterclockwise or clockwise rotating embodiment. If the same housing part is used in the other embodiment, then the other pressure field is used for pressing the sealing plate against the gear wheels.

FIELD AND BACKGROUND OF THE INVENTION

The present invention relates to a hydraulic gear machine, and thereforea gear pump or a gear motor, the gear machine being, in particular, aninternal gear machine as described herein.

In known internal gear machines, an internally toothed hollow gear and asmaller externally toothed gear which engages with the hollow gear arecontained within a chamber of a multipart housing. In order to avoidleakage losses on the high-pressure side of the machine through an axialslot between the gear wheels and a housing part, a sealing plate isarranged on the side of both gear wheels axially between them and a partof the housing, said plate being pressed against the face side of thegear wheels by a pressure field which is connected with the highpressure side. Internal gear machines are known (Federal Republic ofGermany 25 54 960 C2) which have a sealing plate only on one face sideof the two gear wheels. In other known internal gear machines, there isa sealing plate on each face side of both gear wheels.

The pressure field which can act with the high-pressure on the highpressure side of the machine is limited in a plane extendingperpendicular to the axes of the two gear wheels by a packing whichseals off the gap between the sealing plate and the housing part.Depending on whether the packing is inserted into the sealing plate orinto the housing part, it is said that the pressure field is located inthe sealing plate or in the housing part. It is endeavored to produce asealing plate in inexpensive fashion by simple stamping and embossingprocesses. In that case, it is difficult to impart the sealing plate theshape which is necessary for the development of the pressure fieldwithin it. It therefore seems more favorable to provide the pressurefield in the housing part which is adjacent to the sealing plate andwhich is customarily produced as a casting and in which the shapedesired for the development of the pressure field can be producedalready during the casting process.

Generally, the market today requires a clockwise rotating version and acounterclockwise rotating version of a given type of gear machine. It isdesirable to be able to produce both embodiments with the greatestpossible number of identical parts. In the case of the gear machinehaving a sealing plate on both sides of the gears and having a pressurefield developed in each of the two sealing plates, it is possible tomount the same two sealing plates transposed with respect to each otherin the two embodiments, so that the same two sealing plates can be usedfor both versions. In the event that an axial pressure field is arrangedin a housing part which is adjacent to the sealing plate, a differenthousing part has been used up to now, depending on whether the gearmachine was a clockwise or a counterclockwise embodiment.

SUMMARY OF THE INVENTION

The object of the present invention is so to develop a gear machine ofthe type described herein in such a manner that a housing part which isprovided with a pressure field can be used both for a counterclockwiseembodiment and for a clockwise embodiment.

According to aspects of the invention a second pressure field is presentin the housing part and the first housing part is located only on theone side and the second housing part only on the other side of a centerplane which is defined by the axes of rotation of the two gear wheels,so that a piece of the housing part is still present between the twopressure fields. In a concrete embodiment of a gear machine, of course,only one of the two pressure fields is in each case limited by a packingand acted on by the high pressure on the high pressure side of themachine. The second pressure field is recognizable merely by the factthat the housing part is provided also to receive a packing at a placeother than that used at the time. Due to the fact that there is still apiece of the housing part present between the two pressure fields,assurance is had that a packing which is intended to limit one of thetwo pressure fields can be well supported over its entire circumferencein a plane extending perpendicular to the axes of the two gear wheels.Depending on whether the housing part is used for a counterclockwise orfor a clockwise rotating gear machine, the one or the other pressurefield is limited with a packing and used to press the adjacent sealingplate against the gear wheels.

According to a feature of the invention, the second pressure field isarranged symmetrical to the first pressure field with respect to thecenter plane so that the same conditions are present with respect to thepressure field regardless of the direction of rotation of the machine.

In a known internal gear machine having a single pressure field in ahousing part, the limiting line of the pressure field is developed in aregion thereof as a circular arc the center point of which lies on theaxis of the internally toothed gear wheel developed as a hollow wheeland in a region thereof as a circular arc the center point of which lieson the axis of the externally toothed gear wheel. Furthermore, in theregion of the tooth engagement of the two gear wheels, the pressurefield extends beyond the center plane defined by the two axes of thegear wheels. In order to at least partially compensate for the loss ofsurface which has occurred due to the limiting of the pressure field toonly one side of the center plane, towards the center plane, adjoiningan outer region of the limiting line developed as circular arc, there isa portion of the contour the distance of which from the center point ofthe circular arc is greater than the radius of the arc. In this way, acomplete equalization of surface is thus created in the tooth engagementregion, so that the force acting on the sealing plate, assuming the samepressure, corresponds to the force in the known gear machine.

In order to be able, on the one hand, to arrange the pressure fieldssymmetrically to the center plane and, on the other hand, to be able toact with pressure on the sealing plate in the region of the toothengagement on both sides of the center plane, there is present, withinthe engagement region of the two gear wheels, between the first pressurefield and the second pressure field, a third pressure field in thehousing part, which field extends on both sides of the center plane,this third pressure field being acted on by high pressure together ineach case with one of the other two pressure fields.

A development of the hydraulic gear machine which is particularlyfavorable with respect to a small number of different parts for acounterclockwise and a clockwise embodiment is also provided wherein thehousing of the gear machine consists essentially of a middle part, whichhas a low-pressure connection and a high-pressure connection andcloses-off a chamber having two gear wheels which mesh with each otherin a direction perpendicular to the axes of the gear wheels, and of twocovers both of which are developed symmetrically with respect to acenter plane defined by the axes of the two gear wheels. It is thenpossible to construct a counterclockwise embodiment and a clockwiseembodiment of the gear machine using the same parts. In the oneembodiment, as compared with the other embodiment, only the middle partis so installed that in each case the other side faces the same cover.Two sealing plates between the covers and the gear wheels aretransposed. In order to require only one hole in one cover for thefilling-piece pin, the filling-piece pin is mounted in the center planein one cover, particularly if an axial pressure field is not present ina housing part but in a sealing plate.

For a good sealing of the pressure field with respect to the axial slotbetween a sealing plate and the adjacent housing part, it isadvantageous if an elastomer packing which limits the pressure fielddependably retain its position on the edge of the pressure field. Thisincludes it not wandering outward into the axial slot but also notarching inward. From Federal Republic of Germany OS 16 53 837 aninternal gear machine is known in which, by means of a support ringconsisting of a high-strength plastic or metal, an elastomer packing isto be prevented from traveling into a slot. In order further to increasethe assurance against travel of the elastomer packing into an axial slotpresent between a sealing plate and a housing wall, it is provided thatthe support ring be open and have two ends which overlap. Thus, thesupport ring is able to equalize the tolerances of the pressure field onthe outer circumference as well as the tolerances of the support ringitself and to apply itself, without radial slot, against a limiting wallof the pressure field. Such a gear machine can therefore be used withina hydraulic system having very high operating pressures. By features ofthe invention the result is obtained that the operating pressure comesbelow the packing so that a very good sealing effect and a very goodcompensation of the force acting from the gear side on a sealing plateare obtained. Due to the individual projections on the innercircumference of the elastomer packing, the latter is still supported onthe inner wall of the groove receiving it even if the groove is madewider than the packing itself and therefore can be produced veryeconomically. In case the groove is produced by a machining process, achip-removing tool having a diameter corresponding to the larger widthof the groove can namely be used, which permits a higher in-feed speed.Furthermore, such wide grooves can be easily produced other than bymachining, for instance, by pressure casting.

As already indicated, it is favorable for a sealing and compensationeffect if the operating pressure arrives below the packing and if inthis way the elastomer packing is pressed with a force dependent on theamount of the operating pressure against the sealing plate or thehousing part adjacent to the sealing plate. On the other hand, it isfavorable for a reliable positioning of the elastomer packing, for it torest in axial direction both on the sealing plate and on the housingwall.

BRIEF DESCRIPTION OF THE DRAWINGS

With the above and other advantages in view, the present invention willbecome more clearly understood in connection with the detaileddescription of preferred embodiments, when considered with theaccompanying drawings, of which:

FIG. 1 is a sectional view of a first embodiment through the planedefined by the two axes of the gear wheels;

FIG. 2 is a cross section along the line II--II of FIG. 1;

FIG. 3 is a cross section along the line III--III of FIG. 1, a coverpart of the housing being shown partially in plan view;

FIG. 4 shows, by way of comparison, a pressure field according to FIG.3, with a traditional pressure field;

FIG. 5 is a partial section along the line V--V of FIG. 3;

FIG. 6 is an enlarged view of the portion VI in FIG. 3;

FIG. 7 shows in unmounted condition a support ring for an elastomerpacking surrounding a pressure field;

FIG. 8 is a partial section through a second embodiment lying in asectional plane corresponding to the sectional plane of FIG. 1;

FIG. 9 shows the second embodiment in an axial view, from the gearwheels, on a sealing plate and a cover part; and

FIG. 10 is a section along the line X--X of FIG. 9.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The internal gear pump shown in FIGS. 1 and 2 has a housing 10 which isformed of an annular middle part 11 which radially encloses a pumpchamber 12, a first cover part 13, and a second cover part 14. The twocover parts 13 and 14 limit the pump chamber 12 in axial direction. Themiddle part 11 grips around the two cover parts 13 and 14 in the regionin each case of an outer milling 15. The cover part 13 has a continuousbore 16 into which a plain bearing 17 is pressed. With the bore 16 thereis aligned a blind hole 18 in the cover part 14, into which hole a plainbearing 17 is also pressed. In the two plain bearings 17 a drive shaft19 of the pump is supported. An externally toothed pinion 20 is fastenedwithin the pump chamber 12 on the drive shaft 19 or is made in one piecewith it. The pinion is located within an internally toothed hollow gear21 the axis of which is eccentric to the axis of the pinion 20 and whichis mounted on its outer circumference in the middle part 11 of thehousing 10. In the region on both sides of a center plane 22 which isdefined by the two axes of the pinion 20 and the hollow gear 21, the twogears mesh with each other, a crescent-shaped free space 23 beingfurthermore present between them.

This free space 23 is filled up approximately one half by a bipartitefilling piece 24 which lies against the teeth of the pinion 20 and ofthe hollow gear 21 and rests against a flat on a filling-piece pin 25.The latter passes through the free space 23 in the center plane 22 andis rotatably supported in two blind holes, aligned with each other, inthe cover parts 13 and 14 on both sides of the pump chamber 12. Theaxial length of the filling piece 24 agrees with the axial length of thetwo gears 20 and 21.

At diametrically opposite places, a suction channel 26 and a pressurechannel 27 debouch into the pump chamber 12, the diameter of the suctionchannel 26 being larger than the diameter of the pressure channel 27.The hollow gear 21 has holes 28 which extend radially from the inside tothe outside in the tooth gaps, through which holes a hydraulic fluid canpass from the suction channel 26 into the free space 23 and from thereinto the pressure channel 27.

The pump of FIGS. 1 and 2 is so constructed that the pinion 20 must, inoperation, be driven in clockwise direction as viewed in FIG. 2. Thehollow gear 21 then also turns in clockwise direction. Hydraulic fluidpresent in the tooth gaps travels, together with the tooth gaps, alongthe filling piece 24 and passes into the tooth-engagement region of thetwo gear wheels. There, the hydraulic fluid is forced through the holes28 in the hollow gear 21 into the pressure channel 27. At the same time,hydraulic fluid is drawn through other holes 28 out of the suctionchannel 26 into the free space 23.

For a high efficiency of the pump, a good axial sealing of thehigh-pressure side of the pump is necessary, which side can be limitedby a region of the pump chamber 12 within which the filling piece 24 islocated and within which, adjoining the filling piece, the two gearwheels gradually engage further and further into each other. For a goodseal, a sealing plate 35 is arranged between the gear wheels 20 and 21and each cover part 13 or 14, the plate being pressed axially againstthe gears 20 and 21 by a pressure field 36 present between it and thecorresponding cover part 13 or 14. Each sealing plate 35 closelysurrounds the shaft 19 and the filling-piece pin 25 and is therebysecured in its position in a plane perpendicular to the axis of thedrive shaft 19. A pressure field 36 is formed by a recess in the coverpart 13 and 14. As can be noted further from FIG. 3, it has ahalf-crescent shape and extends approximately from the foot of thefilling piece 24 on the filling-piece pin 25 to close to the centerplane 22. It is essential now that in each cover part 13 and 14, on bothsides of the center plane 22, there is a recess 36, the two recesses 36of each cover part being developed as mirror images of each other withrespect to the center plane 22. Both terminate at a distance from thecenter plane 22, so that in their region a piece 37 of the correspondingcover part is still present between the two recesses 36. The outercontour of a recess 36 is formed essentially by four sections, a firstsection 38 being a circular arc the center point of which lies on theaxis of the pinion 20. A second section 39 is also a circular arc, thecenter of which, however, lies on the axis of the hollow gear 21. Thiscircular arc passes tangentially to the center plane 22 into a straightline 40 which can be considered the third section. A section 41 connectsthe section 38 in the region of the center plane 22 with the section 40.A section 42 connects the arcs 38 and 39 at their ends spaced away fromeach other, the section 42 being also in part a straight line.

In FIG. 4, alongside the center plane 22 and a portion of a recess 36,the outer contour of a pressure field of a known internal gear pump isindicated by a dashed line. It can be seen that this pressure fieldextends beyond the center plane 22, while a pressure field of aninternal gear pump in accordance with the invention is limited to oneside of the center plane and maintains a distance from it in the regionof the tooth engagement. In the case of the known pressure field, thecircular arc 39 is continued up to the center plane 22. By theenlargement of the radial extent of a pressure field of an internal gearpump in accordance with the invention in the region of the section 40,the reduction of the pressure field in the region of the center plane 22is approximately compensated for. For the action of the pressure thereis thus available in the region of the center plane 22 substantially thesame area as in the case of a known internal gear machine, so that asealing plate 35 is pressed there against the gears also withapproximately the same force, assuming the same high pressure.

The two cover parts 13 and 14 of the internal gear pumps shown aredeveloped symmetrically with respect to the center plane 22 not onlywith regard to the recesses 36 but in their entirety. They can thereforebe used both for a pump driven with counterclockwise rotation and a pumpdriven with clockwise rotation. As a whole, the two embodiments of apump can be constructed with the same parts. The center plane 22,together with the two sealing plates 35 and the filling piece 24, ismerely assembled to the cover parts 13 and 14 turned 180 degrees aroundan axis passing through the two axes of the gears 20 and 21 and lying inthe center plane 22.

Furthermore, in the one embodiment, the one recess 36 and in the otherembodiment the other recess 36 of a cover part are sealed off by asealing arrangement from an axial slot between the corresponding sealingplate 35 and the corresponding cover part 13 or 14. In the embodiment ofFIGS. 1 to 7, a groove 43 which has the same depth and width over itsentire extent is present in order to receive the sealing arrangement atthe edge of each recess 36. Into the groove 43 there is inserted anelastomer packing 44, which, as can be noted from FIG. 5, has a Z-shapedprofile in cross section with two end profiled sections 45 and 46 and amiddle profiled section 47. The two end profiled sections 45 and 46 areperpendicular to the sealing plate 35, the profiled section 46, which ispresent on the outer wall of the groove 43, resting axially on thebottom of the groove 43 and the further inward profiled section 45resting axially against the sealing plate 35. The end profiled section46 and the middle profiled section 47 of the elastomer packing 44 areentirely within the groove 43. Within the latter, the elastomer packing44 has individual nubs 48 semicircular in axial view which are spacedfrom each other and protrude from the inner circumference of the middleprofiled section 47 and support the elastomer packing 44 on the innerwall of the groove 43. The nubs 48 are at the same distance from thebottom of the groove 43 as the middle profiled section 47 radiallyinward of the profiled section 46. The hubs 48 are therefore notdirectly connected to the profiled section 46, so that a continuouslysurrounding pressure surface 44 is present on the elastomer packing 44radially inward of said section. From the high-pressure side of thepump, hydraulic fluid flowing through holes 35A in a sealing plate 35into a recess 36 can thus pass between the hubs 48 on the rear of theelastomer packing 44 and act with pressure on the packing in the regionof the pressure surface 49 so that the elastomer packing 44 is pressedagainst the sealing plate 35 with a pressure which differs depending onthe height of the pressure on the high-pressure side of the pump. On theother hand, the elastomer packing rests radially inward and outward inthe groove 43, so that packing reliably retains its position.

In order that the elastomer packing 44 does not travel into the axialslot 50, extending from a pressure field 36, between a sealing plate 35and a cover part 13 and 14, a support ring 51 of plastic is providedwhich has a rectangular cross section and is arranged in a regionradially outside the first end-profiled section 45 and axially betweenthe middle profiled section 47 of the elastomer packing 44 and thesealing plate 35. As can be clearly noted from FIG. 7, the support ring51 is a so-called open support ring having two ends 52 which overlap ina plane parallel to the sealing plate 35 in the straight region of thesection 42 of the outer contour of a recess 36 relatively far.Overlapping in a plane parallel to the sealing plate 35 in thisconnection means that upon advance in such plane one passes over bothends 52. Between the two ends therefore, there is no separation jointvisible from the inside of a pressure field 36, extending along thesupport ring. The support ring is, of course, adapted to the outercontour of a recess 36 so that the two overlapping ends 52 are presentalso in the region of a straight section of the support ring 51.Tolerances in the outer circumference of a pressure field as well astolerances of the support ring itself can be counteracted by it becauseof its open shape so that it can apply itself radially without gapagainst the wall of a cover part 13 or 14.

In the embodiment of FIGS. 1 to 7, two mirror-image elastomer packings44 are required, one of which is to be inserted into the cover part 13and the other into the cover part 14. In the case of a pump driven withcounterclockwise rotation, the arrangement between cover parts andelastomer packing is precisely the opposite as in the case of a pumpdriven with clockwise rotation.

The embodiment in accordance in accordance with FIGS. 8 to 10 hasfundamentally the same construction as the embodiment in accordance withFIGS. 1 to 7. Therefore, in the sectional view of FIG. 8, whichcorresponds to the sectional view of FIG. 1, only a small part of thepump is shown. It is clear from FIG. 9 that, also in this embodiment,there are present in the cover parts 13 and 14, of which the cover part14 is shown in FIG. 9, two recesses which are symmetrical to each otherwith respect to the center plane 22. However, the two recesses 36 are,in the region of the tooth engagement of the two gears 20 and 21, at agreater distance from the center plane 22 than the two recesses 36 ofthe embodiment shown in FIGS. 1 to 7. As a result, the piece 37 iswider. To be sure, each cover part 13 or 14 now has, within the regionof the part 37 and at a distance from the recesses 36, a circular recess60 which is symmetrical on both sides of the center plane 22. Thisrecess is connected with the high-pressure side of the pump via an axialbore-hole 61 which is present in the sealing plate 35 adjacent to thecorresponding cover part, debouches into the recess 60, and extends froma recess 62 on the side surface of the sealing plate 35 facing thegears, it being connected with the high-pressure side whether the pumpis operated with counterclockwise rotation or with clockwise rotation.In the embodiment rotating in opposite direction from FIG. 9, there isnamely associated with the cover part 14 the sealing plate 35 which nowis adjacent to the cover part 13 (not shown), while the sealing plate 35shown in FIG. 9 is associated with the cover part 13. The two sealingplates are developed symmetrically to each other with respect to thecenter plane 22 insofar as they viewed, placed alongside of each other,in the direction towards the same side facing towards or away from thegears.

As can be noted from FIG. 9, a sealing plate 35 covers substantiallyonly the high-pressure side of a pump, while the low-pressure side iskept free, so that no rubbing can take place there between the gears anda sealing plate, which would reduce the efficiency of the pump. In aspecific counterclockwise or clockwise embodiment of the pump, there areactive in each case the pressure field 60 and the pressure field 36which is covered by the sealing plate 35 in an axial view of the gears.Only these two pressure fields are sealed off also with an elastomerpacking 63 at the axial slot between the sealing plate 35 and thecorresponding cover part. In the embodiment of FIGS. 8 to 10, theelastomer packing is a simple rectangular packing the axial dimension ofwhich is less than the depth of a recess 36 or 60 and which thus can beacted on, on its rear side, by the pressure prevailing in the pressurefield and be pressed against the sealing plate 35.

We claim:
 1. A hydraulic internal gear machine (pump or motor) which isoperable only in one direction of rotation and which comprises a housingin which there are a high-pressure connection and a low-pressureconnection and which has a middle part, said middle part has thehigh-pressure connection and the low pressure connection, said middlepart closes off a chamber having a hollow gear and a pinion meshingtherewith in a direction perpendicular to the axes of the two gears,and, said middle part is formed asymmetrically with respect to a centerplane defined by axes of the two gears, and two cover parts, betweenwhich the middle part is located, which has a sealing plate arrangedaxially between the two gears and a cover part and which has in ahigh-pressure region a pressure field which can be acted on by highpressure, is open toward the sealing plate, and is present in at leastone of the two cover parts, wherein:in the one cover part there is asecond pressure field which is connected to the low-pressure side; thefirst mentioned pressure field is located only on the one side and thesecond pressure field only on the other side of the center plane definedby the axes of rotation of the two gears so that pieces of the coverpart are still present between the two pressure fields; and the twocover parts are together developed, symmetrically indifferent indirection of rotation with respect to the center plane.
 2. A hydraulicinternal gear machine according to claim 1, whereinthere are twopressure fields in each cover part, and said sealing plate is asymmetricto the center plane and is located between the two gears and each coverpart.
 3. A hydraulic internal gear machine according to claim 1,whereina pressure field has as a limiting line in one region a circulararc, the center point of which lies on the axis of the hollow gear; andtowards the center plane, in the region of engagement of the two gears,the circular arc is adjoined as a limiting line by a contour section,the distance of which from the center point is greater than the radiusof the circular arc.
 4. A hydraulic internal gear machine according toclaim 3, wherein the contour section is linear and tangentially adjoinsthe circular arc.
 5. A hydraulic internal gear machine according toclaim 1, whereinwithin the region of engagement of the two gears betweenthe first pressure field and the second pressure field there is locatedwithin the cover part a third pressure field which extends on both sidesof the center plane; and said third pressure field can be acted on byhigh pressure in each case together with one of the other two pressurefields.
 6. A hydraulic internal gear machine according to claim 5,wherein the third pressure field is symmetrical with respect to thecenter plane.
 7. A hydraulic internal gear machine according to claim 5,wherein the third pressure field is circular.
 8. A hydraulic internalgear machine according to claim 7, wherein the sealing plate has anopening, particularly a hole, debouching into the third pressure fieldand a recess in its side surface facing the gears which extends awayfrom the center plane towards the high-pressure side and from which theopening extends.
 9. A hydraulic internal gear machine according to claim1, wherein a pressure field is located within a recess in the coverpart.
 10. A hydraulic internal gear machine according to claim 1,wherein a filler piece which is located between an internally toothedhollow gear and an externally toothed pinion is supported on afiller-piece pin which is mounted in the center plane in a cover part.11. A hydraulic internal gear machine according to claim 1, wherein anaxial slot extending from high-pressure pressure field between thesealing plate and a cover plate is sealed off by an elastomer packing.12. A hydraulic internal gear machine according to claim 4, wherein thethird pressure field is circular.
 13. A hydraulic internal gear machineaccording to claim 5, wherein the sealing plate has an opening,particularly a hole, debouching into the third pressure field and arecess in its side surface facing the gears which extends away from thecenter plane towards the high-pressure side and from which the openingextends.
 14. A hydraulic internal gear machine according to claim 6,wherein the sealing plate has an opening, particularly a hole,debouching into the third pressure field and a recess in its sidesurface facing the gears which extends away from the center planetowards the high-pressure side and from which the opening extends.
 15. Ahydraulic internal gear machine according to claim 12, wherein thesealing plate has an opening, particularly a hole, debouching into thethird pressure field and a recess in its side surface facing the gearswhich extends away from the center plane towards the high-pressure sideand from which the opening extends.
 16. A hydraulic internal gearmachine according to claim 5, wherein a pressure field is located withina recess in the cover part.